Motorcycles are a popular means of recreation and transportation for a number of people. Being a two-wheeled vehicle, the suspension of the motorcycle is very important for proper operation. If the suspension is not working properly, the handling characteristics of the motorcycle and the way it absorbs bumps are dramatically affected. In order to insure that the suspension is working properly it is imperative that the forks must be aligned to be very parallel with each other. It is well known that every time the front wheel is removed and replaced the forks need to be aligned which in most cases is done by working the suspension up and down a few times before tightening the fork leg to the front axle. Additionally, some forks have been found to be out of alignment when received from the factory.
This misalignment largely results when the forks are not parallel along their length. This property will be referred to in this discussion as “parallelism”. Parallelism can be measured from the centerline of each fork at various points along their lengths. However, this can be somewhat difficult, as the forks are generally configured as cylindrical tubes. Determining the center point can be difficult on a curved object, and thus a gauge configured to mate with a curved surface can greatly simplify an alignment operation.
The structure of a motorcycle fork can be more easily understood with reference to FIG. 4 which shows a very simplified view of the main elements of a motorcycle fork. No attempt has been made to draw the various elements in proper scale or proportion to each other.
FIG. 4 shows a front plan view of a motorcycle fork 52, with the front wheel 54 mounted on axle 56. The fork 52 includes two fork tubes 58, which connect to two fork legs 60, which are sometimes manufactured to be telescopically retractable within the fork tubes 58. The fork 52 can also be thought of as having a left fork 62 and a right fork 64, which are joined by various clamps to maintain their parallelism. A top clamp 66, and lower clamp 68 (also called a triple tree), connect the left fork 62 and right fork 64, in addition to the axle 56, which is held in axle clamps 72 by pinch bolts 70. Thus, there are three cross-pieces that join the left fork 62 and right fork 64 and maintain the parallelism between them. The spacing at the top clamp 66, and lower clamp 68 and axle clamps 72 are largely fixed, but may be adjustable to some degree. Thus, alignment of the forks 52 includes measuring the distance between centerlines of the fork tubes 58 and fork legs 60, and fastening the pinch bolts 70 of the axle clamps 72 to lock them into place.
As referred to above, determining the centerline of the curved tubes 58 and legs 60 can be difficult using linear measuring devices, such as tape measures, etc. Thus there exists a need for a gauge that can easily establish the proper spacing between the fork legs 60 and can be easily used to place the forks 52 into parallel alignment, so that they may be locked into place.